Fighting the U-boats

Norwegian Naval forces

The Norwegian Navy at the beginning of the war in 1940 consisted of 1 minelayer, 1 escort and 9 submarines.
Later the British gave to Norwegians 6 destroyers, a few corvettes and
3 submarines, as the Norwegians lost almost all their fleet during the German invasion
when the Germans captured 2 battleships, 4 submarines (3 were scuttled by their own
crews) and other smaller vessels.

One submarine, B-1, managed to escape and sailed to England. The Norwegian Navy
participated in many operations in the North Sea, the Atlantic and the Arctic Ocean.

Worth to be mentioned is that Norway had the oldest battleships during WWII, the
Harald Haarfagre and Tordenskjold were build in 1897 and used as training hulks. They also had 2 coast defence vessels (Eidsvold and Norge). The former 2 were captured by the Germans while the others were sunk at Narvik on April 9, 1940 during the invasion of Norway with the loss of 276 men (105 survivors).

U-57 sank after accidentally colliding with the Norwegian merchant ship SS Rona on 3 September, 1940 in the Baltic Sea. She was later raised and returned to service.

Almost the entire strength of the Royal Norwegian Navy was dedicated to the Battle of the Atlantic. Only two submarines and a flotilla of motor torpedo boats (MTBs) were not employed in the anti-submarine war.

Norwegian Naval successes

The Norwegian submarine Ula sank with a spread of 4 torpedoes the U-974 on 19 April, 1944 near Karsmund.

The Norwegian Flower class corvettePotentilla is reported to have sunk the U-184 on 20 November, 1942 in the Atlantic. This attack was in fact against the
U-264 inflicting no damage.

It has been reported that a few U-boats were sunk by mines near Norway laid by Norwegian vessels (I have no U-boat numbers to match this with though).